Metronidazole against bacteria

The antibiotic metronidazole is used to treat bacterial infections as well as diseases caused by protozoa (unicellular organisms). Depending on the infection, it is available in the form of tablets, suppositories and infusions as well as a cream, gel or ointment. Side effects such as headache, gastrointestinal discomfort, or redness may occur while taking metronidazole. Find out more about the effects, side effects and dosage of metronidazole here.

This is how metronidazole works

Metronidazole is a prescription antibiotic belonging to the nitroimidazole group. It is used to treat infections caused by anaerobic bacteria or protozoa.

Active ingredients from the group of nitroimidazoles are metabolized by bacterial enzymes to so-called nitroso radicals. These attack the DNA of the bacteria and lead there to strand breaks. As a result, the cell dies and the infection can be effectively combated.

Application areas of the antibiotic

Metronidazole is used to treat bacterial infections of the mouth and jaw, ear, nose and throat, gastrointestinal (Helicobacter pylori) and female genitalia. It is also used in bone and joint and leg vein inflammation and heart infections. In addition, the drug can prevent an infection in operations in the gastrointestinal tract and on the female genital organs.

In addition, metronidazole can treat inflammation of the vagina or the male urethra caused by trichomonads (flagellates). The transfer takes place primarily via sexual intercourse. Therefore, the sexual partner should be examined for the pathogens and treated if necessary.

In addition, metronidazole can also be used in a number of other diseases - especially the gastrointestinal tract and the female genital organs. These include the intestinal diseases Lambliasis (Giardiasis) and Amöbiasis (amoebic dysentery) as well as bacterial vaginosis. Metronidazole is used as an ointment or cream for the treatment of skin diseases such as rosacea or perioral dermatitis as well as eczema and abscesses.

Side effects of metronidazole

The intake of metronidazole can be associated with a variety of side effects. Decisive in addition to the dosage and the dosage form of the antibiotic.

Tablets, infusions or suppositories:

Taking Metronidazole may cause side effects such as mouth or tongue irritation, taste disorders and tongue coating. It can also cause gastrointestinal symptoms such as diarrhea, abdominal pain and nausea and vomiting. In addition, patients often experience darkened urine during treatment.

Occasionally side effects such as headache, dizziness, sleep disturbances, weakness, drowsiness, numbness, tingling, depression, seizures, coordination disorders, and nervous disorders have been reported. In addition, blood count changes or phlebitis may occur.

In rare cases, side effects such as allergic reactions and redness, bladder infections, urinary disorders and bladder weakness, genital mycosis, blurred vision and abnormal liver function may continue to be noticeable.

Local application on the gums:

Applying metronidazole to the gums may increase the sensitivity of the teeth. In rare cases, side effects such as gum and gingivitis, as well as taste disorders may occur. It can also cause dizziness, dysphagia, headache, nausea and vomiting, as well as skin reactions.

Local or vaginal use:

In rare cases, side effects such as redness, itching or burning may occur.

Dosage of metronidazole

Depending on the severity of the disease, the dosage of metronidazole can vary greatly. Therefore, the following dosage information is only a general guideline. You should always discuss the exact dosage with your doctor. Without medical consultation you should not take the antibiotic for more than ten days at a time.

Uncomplicated infections can be treated by giving three times 0.2 grams of metronidazole or less for five to seven days. If the active ingredient is dosed higher (one to two grams), a period of one to three days may be sufficient.

For complicated infections, between 1.6 and 2 grams of metronidazole are administered initially followed by one gram for five to seven days. Complicated infections include inflammation of the lining of the uterus, ovaries and peritoneum, inflammation of the mouth and jaw, and inflammation of the ear, nose and throat.

Bacterial vaginosis and trichomoniasis

Bacterial vaginosis or trichomoniasis in adults may be treated by a single dose of two grams of metronidazole. Alternatively, if bacterial vaginosis is used, it is recommended to take one gram each of the antibiotic for seven days. It is usually taken by two or three single doses daily.

Following the same regimen, trichomoniasis can be administered between 0.8 and 1.6 grams of metronidazole.

In children, the respective dose is determined individually by the attending physician depending on body weight and disease. Most children get between 20 and 30 milligrams per kilogram of body weight. The maximum dose per day is 2 grams. For the treatment of rosacea and periodontitis, metronidazole should not be used in children.


Metronidazole should not be used if hypersensitivity to the active substance is present. In addition, the antibiotic should be used in patients with severe liver disease only after a careful benefit-risk analysis. If the antibiotic is taken in tablet form, the liver values ​​must be checked at regular intervals.

Metronidazole may also be used only after a careful benefit-risk analysis in diseases of the nervous system, such as epilepsy, the brain and spinal cord, and blood disorders. If the composition of the blood is incorrect, the physician must decide individually whether creams or ointments containing metronidazole may be used to treat rosacea.


Similar to the side effects, the interactions depend on the particular dosage form. Which interactions can occur in your case, please clarify with your doctor. Alternatively, a look in the leaflet can help you further.

In general, interactions may occur when metronidazole is taken with any of the following drugs or agents:

  • sleeping pills
  • Curmarinderivate
  • lithium
  • phenytoin
  • cimetidine
  • disulfiram

Patients on certain anticoagulants should be readjusted if they are taking metronidazole. This is necessary because the antibiotic can enhance the anticoagulant effect of the drugs.

During treatment with metronidazole you should abstain from alcohol. Otherwise, interactions such as headache, dizziness, nausea and vomiting may occur.

pregnancy and breast feeding period

Metronidazole should not be taken during pregnancy. Until now, it could not be ascertained with certainty whether the drug could cause damage to the unborn child. Therefore, especially in the first three months of pregnancy, the antibiotic should be used only for life-threatening infections. Thereafter, the drug may be prescribed only after a careful benefit-risk analysis. Whenever possible, use ointments, creams or gels instead of tablets.

Metronidazole should also not be taken during breast-feeding, as the active substance passes into breast milk. If ingestion is mandatory, breastfeeding should not be stopped during this time. If only a gel is applied in the mouth area, an interruption of breastfeeding is not necessary.

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